Unexpected outages, intense heat behind ISO-NE Labor Day price spike

ISO-NE’s Monday conditions show how quickly errors in load forecasting and unplanned outages can translate into price spikes in the region’s real-time market.

The ISO planned for 22,800 MW of demand at 4:30 p.m. on Monday, but real demand topped 23,100 MW, according to the grid operator’s posted data. When some generators were unavailable to provide service, the ISO resorted to emergency power imports as prices spiked.

ISO-NE did not detail which power plants were unexpectedly offline, but they appear to be natural-gas fired plants, judging from a dip in gas generation around the time of the price spike.

While the ISO declared an emergency power watch, the system was not brought to the absolute brink. Operators were not forced to ask consumers for voluntary conservation measures, Blomberg said, though they monitored the situation and “could have issued an appeal if conditions had deteriorated.”

“Conditions improved rapidly as demand began to decline in the late afternoon and offline generators were able to come online,” Blomberg wrote in an email.